Brandon Santana is being sought by the NYPD after escaping police custody in Brooklyn early this morning.Photo: DCPI

Victim Alex Santiago was killed on Aug. 1, 2010. (Benny J. Stumbo)

An accused murderer dramatically escaped from a Brooklyn police station early this morning after asking a cop to go to the bathroom, authorities said.

The fugitive, Brandon Santana, 24, had been questioned at the the 78th Precinct in Park Slope after his extradition on charges of brutally beating 22-year-old dad to be Alexander Santiago in August 2010 as part of a large gang attack on Santiago and three other men.

He had been extradited from a western state, according to Santiago’s family.

After being questioned, Santana was then taken to a holding cell, according to law-enforcement sources.

An hour later, at 2 a.m. today, Santana requested to use the toilet, sources said.

When the cell door was opened by a cop assigned to keep an eye on him, Santana — who was not handcuffed — shoved that officer, knocking him to the ground, and then fled out the front door of the station house, source said.

Cops are now aggressively searching for Santana. He is 5-foot-11, 200 pounds, with short black hair and brown eyes, and last was seen wearing a brown hoodie, blue jeans and white sneakers, cops said.

The cop whom he knocked down was treated at Methodist Hospital for an elbow injury and released. The escape is now under investigation by the NYPD, according to sources.

Authorities claim that Santana was part of a gang of about 30 people who ambushed Santiago and three other men on Aug. 1, 2010 on 12th Street and Fifth Avenue.

Santana is believed to have bludgeoned Santiago to death with a lead pipe.

Another man was stabbed 20 times — but survived the attack.

Sources said that one of the victims of the ambush — not Santiago — was a confidential witness for authorities. It was not clear if that victim’s status as a witness played a role in the attack.

Santiago’s girlfriend later gave birth to their son, whom she named Alexander Jr.

Two months after Santiago was murdered, a man named Randy Soto was charged with murder, attempted murder, manslaughter, gang assault and weapons charges in the attack. Soto, who turned 25 today, is in custody, and next is due in court on March 20.

Earlier this week, the Brooklyn District Attorney called Santiago’s family and told them that Santana had been apprehended in a western state, and was being held there pending extradition, Santiago’s family told The Post today.

Today, Santiago’s family said, the DA’s office called again to inform them that Santana had escaped hours before.

Anyone with information is asked to call Crime stoppers at 1-800-577-TIPS (8477). The public can also submit their tips by logging onto the Crime stoppers Web site at www.nypdcrimestoppers.com or by texting their tips to 274637 (CRIMES) then enter TIP577.